Cooled Ultrasonic Transducer

Abstract

An ultrasonic transducer comprises a back body, a front body, one or more piezo electric crystal discs sandwiched therebetween, and a central bolt holding the elements together. Cooling air passes into a central bore in the bolt, out the bottom of the bolt, and up through a longitudinal groove in the outside of the bolt to an annulus between the bolt and the piezo electric discs. The air then passes outwardly through radial grooves between the crystal discs and adjoining metal elements.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel ultrasonic transducer construction having provision for improved cooling of the vibration producing elements.

2. Description of the Prior Art

Ultrasonic transducers have been well known for a number of years and have found extensive applications in industry for the welding of plastics and other applications. The most commonly used ultrasonic transducers depend upon piezo electric crystals for generating the desired vibrations when oscillating electrical currents are applied thereto. An example of such an ultrasonic transducer is described in U.S. Pat. No. 3,328,610. When transducers are used continuously, the crystals tend to become quite hot and it has been found necessary to cool them as by passing a flow of air around the outside of the transducer. While this is effective, I have found that substantial heat still tends to build up in the crystals and the efficiency of cooling should be improved if possible.

SUMMARY OF THE INVENTION

In accordance with the present invention the efficiency of cooling an ultrasonic transducer is improved by providing for the flow of cooling fluid such as air through the center of the transducer and then laterally outward in contact with the faces of the crystals. This mode of cooling can be accomplished in a transducer having only a single piezo electric crystal but since the more commonly used transducers employ two stacked crystals, the invention will be described hereinafter with reference to such a transducer.

THE DRAWINGS

In the drawings FIG. 1 is a vertical sectional view, parts being in elevation showing an ultrasonic transducer in accordance with the invention:

FIG. 2 is a cross-sectional sectional view taken along the line 2-2 in FIG. 1;

FIG. 3 is a cross-sectional view taken along the lines 3-3 or 3'-3' in FIG. 1; and

FIG. 4 is a cross-sectional view taken along the line 4-4 in FIG. 1.

THE PREFERRED EMBODIMENT

Referring to the drawings there is shown an ultrasonic transducer T comprising a metal back body 11, a metal front body 13 and a piezo electric crystal means C sandwiched between and in contact with end faces 15 and 17 of such bodies.

A central bolt 19 extends through bores in the bodies 11 and 13 and in the crystal means C and is threaded at its lower end into the bore 21 and in front body 13. The head of bolt 19 bears against the top of back body 11 to hold the elements tightly together.

The crystal means C comprises upper and lower piezo electric crystal discs 23 and 25 and an intermediate metal spacer 27 having opposite faces in intimate contact with the faces of the crystal discs, all three being spaced from bolt 19 so that no electrical contact is made with the bolt. Insulation from the bolt can also be assured by positioning a cylindrical insulator within the annular space 33, with a sufficiently loose fit to permit the flow of air. Discs 23 and 25 can be any desired piezo electric crystal material but the well-known PZT crystal (lead, zirconate, titanate) is preferred.

For cooling the transducer, the bolt 19 is provided with a longitudinal central bore 29 whose upper end is in communication with an air supply conduit 31, and whose lower end opens into the bottom of bore 21. The external surface of bolt 19 is provided with a longitudinal groove 31 which extends from the bottom of the bolt about halfway up so that fluid will flow from bore 29 into bore 21 and then up through groove 31 into an annular space 33 which surrounds the bolt adjacent to the crystal means C.

Each of the bodies 11, 27 and 13 has the faces thereof which are in contact with the crystals 23 and 25 formed with a series of transversely extending radial grooves 35, 37, 39 and 41 which extend from the inner circumferences at such ringlike members to their outer circumferences so that air which has entered the annulus 33 flows radially outwardly in contact with all faces of the crystal elements.

While the preferred embodiment has been described, it is evident that the same type of construction is susceptible to modifications without departing from the principles of the invention. For example, instead of supplying the air through conduit 31, the upper portion of the transducer can be surrounded by an enclosure to which air is supplied for flow from the outside of the transducer to the inside and then out through the longitudinal bore 29 and the conduit 31. It is also evident that the transducer 13 can be supported in any desired way when operating, as by suitable clamps or supporting discs which will permit vibration while maintaining the desired position. It is also evident that the radial grooves can be formed in the crystal elements rather than in the metal bodies.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

I claim:

1. In a fluid cooled ultrasonic transducer comprising a back body; a front body; piezo electric crystal means sandwiched between and in contact with end faces of said back body and said front body; and a central bolt holding together said back body, said front body, and said piezo electric crystal means, the improvement wherein:

said transducer has duct means extending transversely from adjacent said central bolt to the outside of said transducer between said front body and said crystal means, and between said back body and said crystal means, for conducting cooling fluid in contact with said crystal means; and

said central bolt has longitudinal passage means therein communicating with said duct means, said passage means being adapted to conduct cooling fluid.

2. In an ultrasonic transducer in accordance with claim 1, said duct means comprising a plurality of transverse grooves formed in said end faces of said front body and said back body, said bolt being spaced annularly from said piezo electric crystal means to form an annulus communicating with said transverse grooves, and said longitudinal passage means in said bolt communicating with said annulus.

3. In an ultrasonic transducer in accordance with claim 2, said longitudinal passage means comprising a central passage in said bolt, and an external groove in said bolt extending from the end thereof to said annulus, said end of said bolt being located in a bore in said front body and terminating at a point spaced from the bottom of said bore whereby fluid flows between said central passage and said bore and between said bore and said annulus.

4. In a fluid cooled ultrasonic transducer in accordance with claim 2 wherein said piezo electric crystal means comprises a pair of crystals and a spacer therebetween, said spacer having two opposite faces in contact with said crystals, the further improvement wherein: said two opposite faces have transverse grooves therein extending from said annulus adjacent said central bolt to the outside of said transducer for conducting cooling fluid in contact with said crystals. 5. In a fluid cooled ultrasonic transducer in accordance with claim 1, the further improvement of means

coupled to said bolt for supplying a stream of cooling fluid thereto. 6. In a fluid cooled ultrasonic transducer in accordance with claim 2 wherein said back body, said front body and said piezo electric crystal means are all rings having an inner circumference and an outer circumference, the further improvement wherein said grooves extend radially from said inner circumference to said outer circumference of said

bodies. 7. In a fluid cooled ultrasonic transducer in accordance with claim 4, the further improvement wherein said back body, said front body, said pair of crystals, and said spacer are all rings having inner and outer circumferences, the further improvement wherein said grooves extend radially from said inner circumference to said outer circumference of said bodies and said spacer.